Summary/Abstract Most primary care providers (PCPs) (i e. physicians, physician assistants and nurse practitioners) now struggle to meet the complex needs of those adults with two or more chronic health conditions (i e. those who are comorbid) healthcare consumers under typical office visit constraints.1-6 Research has demonstrated that PCPs frequently lack adequate time to monitor consumers' completion of recommended preventive or screening services under traditional medical record systems.2,3,7-10 Although it's well-established that completion rates of most preventive/screening services under paper-based systems are inadequate, our knowledge of how the use of ambulatory electronic health records (EHR) may affect these completion rates for more comorbid adults is virtually non-existent.2,11-17 According to the AHRQ and numerous other groups, this understanding will be crucial to refine better targeted ambulatory EHR functionalities (e g. automatic reminders for indicated tests and procedures, structured data reporting) and guide sustainable policies and practices to impact preventive/screening service completion among vulnerable comorbid adults.10-20 The purpose of these pre-post controlled analyses is to examine the impact of Stage One Medicaid MU adoption of an EHR on changes over time in completion of six preventive/screening services recommended by the U.S. Preventive Services Task Force (USPSTF) 28 for over 3,500 continuously-covered comorbid adult Medicaid beneficiaries and their respective PCPs.